"It wasn't intimidating, no, it was exciting," said the 31-year-old Liverpudlian. "I think that's because I'd guessed they were looking for the right person, so I was excited they thought I could do it."

The prequel, which fans will know takes its title from Morse's closely-guarded first name, is based on a short story by Morse's creator Colin Dexter and is scripted by Russell Lewis, who wrote the Morse spin-off, Lewis.

It sees the young Morse working as a police inspector after being kicked out of Oxford University, and lays the foundations for the Morse we came to know during the original series.

Shaun explained: "You see the beginnings of all the things which made him so popular in his later period; he's struggling with women even then, struggling with work and struggling with himself, but he already has a love of classical music and crosswords, poetry, old cars and beer."

But anyone thinking the title suggests we might see a more open and carefree Morse is mistaken - as the actor revealed his character is just as curmudgeonly in his earlier years.

"It's called Endeavour, but he's very secretive about his name, even then," he said. "That was one of the things I found so interesting about him. Can you imagine being embarrassed by your first name? And having issues of letting people in and keeping everyone at arm's length? We see the beginnings of that, because only a close few get to know his name."